The present invention relates to carrier tapes and in particular to a one piece carrier tape in which the base strip and cover strip are integrally formed.
Carrier tapes are of ever increasing importance in assembly operations in numerous industries including, in particular, the electronic and pharmaceutical industries. The tapes are used, for example, to transport miniature and subminiature electronic components from a components manufacturer to a customer's assembly station where automatic equipment functions to remove the component from the carrier tape and mount the component to a circuit board or the like. The carrier tape (or transfer tape, as it is sometimes referred to) may also function to bring different components to an assembly station in proper order to sequential assembly.
Such carrier tapes are often in the form of a base strip of plastic, foil or paper which is usually covered by a cover strip which is sometimes called the top tape. The base strip is formed with a plurality of cavities or pockets for the components and the cover strip is secured to the base strip to thereby prevent the components from prematurely falling out of the cavities. In the past the base strip and cover strip were most commonly held in place by an adhesive, heat bond or spaced snap-type fasteners. Typical examples of prior art carrier tapes are disclosed in U.S. Pat. Nos. 3,465,874; 3,650,430; 3,700,019; 3,894,896; 3,920,410; and 4,298,120. In recently issued patents 4,733,778 and 4,708,245 carrier tapes are disclosed which utilize a continuous mechanical interlock between the base strip and cover strip to obviate many of the problems associated with the use of the various prior art methods of securing the base strip and cover strip.
To function properly, a carrier tape must securely convey its cargo as required and then, at the proper location, be capable of being quickly and positively opened so that the component may be easily removed from assembly purposes. The tape should afford a degree of protection for the sensitive components to be conveyed therein with respect to contamination, electro-static discharge, temperature change and mechanical shock. In addition, the seal or bond between the tape components must be releasable to a known and consistent value at the unloading point to insure that only the required length of base tape will be exposed.
Prior art tapes utilizing heat activated adhesive or heat bonding techniques present a risk of residue contamination. Further, heat bonding requires the use of relatively high temperatures which may be harmful to the components to be carried. In addition, the use of static-dissipative or conductive additives to prevent or dissipate the build-up of electrostatic charge tends to interfere with the bonding characteristics of adhesives.
The above mentioned recently issued patents disclose a carrier tape wherein integrally formed male and female profiles positioned on the base and carrier tapes interlock with each other to provide a construction which avoid the problems discussed above. Such carrier tapes, however, are formed of two components and hence entail two manufacturing and assembly operations which add to the cost of the product.
In view of the above, it is the principal object of the present invention to provide an improved carrier tape construction in which the base and cover strips are integrally formed with each other.
A further object is to provide such a carrier tape which avoids the use of adhesive and chemical bonding and in which the cover strip and base strip may consistently be secured to one another and separated from each other.
Another object is to provide such a carrier tape which may readily be used on existing equipment with little or no modification.
Yet another object is to provide such a carrier tape which may readily be manually opened and closed so as to facilitate the inspection and replacement of the components carried therein.